Intracardiac QRS electrogram width--an arrhythmia detection feature for implantable cardioverter defibrillators:...

Area of Science:

• Cardiology
• Biomedical Engineering

Background:

• Inaccurate arrhythmia detection in implantable cardioverter defibrillators (ICDs) leads to inappropriate therapy.
• Current ICDs use criteria like cycle length stability and onset suddenness to prevent misdiagnosis.
• Newer ICDs incorporate QRS width to differentiate supraventricular from ventricular tachycardias.

Purpose of the Study:

• To investigate frequency-dependent changes in QRS width at rest and during exercise.
• To determine the impact of physiological conditions on QRS width variability.
• To assess the necessity of reprogramming QRS width parameters based on these variations.

Main Methods:

• Studied 16 patients with ventricular tachycardia or fibrillation.
• Measured QRS width from intracardiac electrograms (EGM) at rest and during symptom-limited exercise.
• Compared measurements from implantation to hospital discharge.

Main Results:

• QRS width showed significantly greater variation during exercise compared to rest (average range 11 +/- 3 ms vs. 7 +/- 3 ms, P = 0.004).
• An increase of >= 4 ms in QRS range was observed in 69% of patients during exercise.
• Reprogramming of QRS width parameters was necessary in 81% of patients.

Conclusions:

• Intracardiac QRS width exhibits significant intraindividual variability under different physiological conditions.
• Exercise testing is essential for capturing these dynamic changes.
• Optimal programming of ICD QRS width parameters requires considering exercise-induced variations.